Connecting bathroom waste pipe to the soil stack

[Lobster]

Hi all

I need to connect a 40mm waste pipe to a soil stack; never had to do this before.

Is it simply a matter of attaching a soil strap boss:

appropriate rubber adaptor inside the boss: first drilled a hole in the side of the stack?

How does this work - is there a seal between the boss and the soil pipe? What size hole to form in the soil pipe - does the 40mm butt up agaist the outside of the pipe, or protrude into it? Or do you try to get it flush with the internal bore of the soil pipe?

The plan would be for the junction to be a few inches below where the toilet effluent enters the stack - is that an issue?

Thanks David

[Tournifreak]

Yes, correct.

Don't let it protrude - this could cause blockages. I've always tried to get the end flush with the wall of the soil pipe. There's no seal built into the boss. The screwfix ones have a sort of tightening clip-thing which holds it in place but does not waterproof the joint. I use solvent-based glue around the boss-soil pipe joint. I've found it best not to attach the rubber adaptor or the waste pipe until the solvent is well and truly cured, otherwise the 'pull' of the waste pipe can dislodge the boss and cause leaks.

That depends on whether the toilet outlet enters on the same side as the waste pipe or not. If opposite sides, allow 200mm minimum. The idea is to avoid "effluent" blocking the outlet of the waste pipe. See the Building Regs Approved Doc PtH:

9 is what you want.

Jon.

[Lobster]

Thanks a lot for this. So basically what you aim at is to attach and seal the waste pipe to the soil pipe before introducing the boss, which essentially just provides mechanical support?

No mine will be at 90 deg to each other, so sounds like that should be OK.

Thanks again David

[Tournifreak]

Not quite what I meant! Let me try again: I've found it best to attach the boss to the soil pipe with solvent weld adhesive. Wait for the solvent to fully cure. Then push in the rubber adaptor and waste pipe.

I would think so, yes. I guess ideally, the waste would enter the soil pipe slightly above the toilet outlet. That would ensure no unmentionables clog the waste outlet!

Jon. Jon.

[Chris Bacon]

Why an adaptor? Can't you use solvent weld?

Gap filling solvent cement.

The ones I've used locate into it.

Not unless it's like this:

| | ____ | | ,' ____ W.C. | |/ ,' | / | / | / | | ============= |

[Lobster]

Thanks. That's two folk mentioned solvent welding... from my limited experience of using this, doesn't it involve materials made from specific type of plastic? I don't know what the soil pipe's made from, but unlikely to be that I'd have thought?

Sounds like this is not the solvent weld liquid I have in from previous job? Never heard of this - who makes it?

Thanks David

[Chris Bacon]

You should use it for joining fittings and pipe, rather than non gap-filling cement. It's for uPVC. You get it in a tube like a big toothpaste tube. I think I bought some Osma stuff. You could see

(page 34).